Valve mechanisms for two-cycle internal combustion engines



April 19, 1955 J. A. slLLS VALVE MECHANIsM FOR Two-CYCLE INTERNAL coMBusTroN ENGINES INVENTOR. Joseph A. Sills Owvw/'Yd Ays.

BY JM.

Filed Aug. 13. 1952 United States Patent O VALVE lVIECHANISMS FOR TWO-CYCLE INTERNAL COMBUSTION ENGINES Joseph A. Sills, St. Charles, lll. Application August 13, 1952, Serial No. 304,083 7 Claims. (Cl. 12S-65) The present invention relates to two-cycle internal combustion engines and more particularly to improved scavenger valve mechanisms therefor. I

In a conventional two-cycle diesel engine, each piston chamber is provided with a scavenger valve mechanism of the poppet type, wherein the poppet valve element moves inwardly into the explosion dome provided at the outer end of the piston chamber to effect opening of the associated exhaust port so that the llame sweeps along the connecting valve stem through the exhaust port into the communicating exhaust passage.

Not only is this opening movement of the poppet valve element into the explosion dome objectionable from the standpoint that the connecting valve stem is heated by the flame in direct contact therewith, causing expansion and warping of the parts, but the valve stem partially fills the exhaust port preventing immediate release of the pressure in the piston chamber as the poppet valve element is moved into its open position. The lastmentioned criticism becomes very serious in two-cycle diesel engines of the high-speed and high-compression ratio type, as it is essential to efficient operation of an engine of this character that the scavenger valve moves to a fully open position in an extremely short time interval, whereby scavenger valve mechanism of the poppet type is not at all well-suited to use in an engine of the type mentioned.

Accordingly, it is a general object of the present invention to provide in a two-cycle internal combustion engine, scavenger valve mechanism of improved construction and arrangement that is movable from its open position into its fully closed position with a moderately fast action and that is movable from its closed position into its fully open position with an exceedingly fast action.

Another object of the invention is to provide in a two-cycle internal combustion engine, improved scavenger valve mechanism that includes a stationary valve plate cooperating with the outer end of an associated piston chamber and provided with an exhaust port therein, and a movable valve element cooperating with the valve plate and movable between open and closed positions with respect thereto, wherein movement of the valve element a short distance away from the valve plate and in a direction away from the adjacent outer end of the piston chamber completely opens the exhaust port.

A further object of the invention is to provide scavenger valve mechanism of improved and simplied construction and arrangement comprising a minimum number of operating parts.

Further features of the invention pertain to the particular arrangement of the elements of the diesel engine and the scavenger valve mechanism, whereby the aboveoutlined and additional operating features thereof are attained.

The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the following specification taken in connection with the accompanying drawing, in which Figure 1 is a fragmentary longitudinal vertical sectional view of the upper portion of a diesel engine incorporating scavenger valve mechanism and embodying the present invention;

Fig. 2 is a fragmentary plan view of the engine and valve mechanism;

Fig. 3 is a fragmentary vertical sectional view of the upper portion of the valve mechanism, taken in the direction of the arrows along the line 3-3 in Fig. 2,

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illustrating the arrangement of the operating cams therefor; and

Fig. 4 is a vertical sectional view of the upper portion of the valve mechanism, taken in the direction of the arrows along the line 4-4 in Fig. l, illustrating the construction of the stationary valve plate thereof.

Referring now to the drawing, there is illustrated a fragmentary portion of a diesel engine 10 incorporating scavenger valve mechanism 11 and embodying the features of the present invention. The diesel engine 10 is of a conventional two-cycle type and comprises a block 12 that may be provided with three piston chambers, one of which is illustrated at 13. The piston chamber 13 receives an associated reciprocating piston 14 provided with a convex upper end 15 and operatively connected at the lower end thereof to an associated crankshaft, not shown. A number of circumferentially arranged fresh air intake ports 16 are formed in the block 12 and communicating with the piston chamber 13, when the piston 14 is in its lower position. Also the engine 10 comprises a head 17 that is provided with three exhaust cavities 18, etc., that are respectively operatively associated with the three piston chambers 13, etc.; which exhaust cavities 18, etc., are commonly connected to an exhaust passage provided in an exhaust manifold, not shown, in a conventional manner.

The scavenger valve mechanism 11 comprises a stationary valve plate 19 arranged in the exhaust cavity 18 and closing the outer end of the piston chamber 13; the valve plate 19 having a substantially inverted cupshape and including a top wall 20 and a side wall 21 terminating in an outwardly directed annular rim 22. Preferably the valve plate 19 is formed of one-piece integral construction of an appropriate temperatureresistant steel, and the inner surface thereof is provided with a concave explosion dome 23 opening directly into the adjacent outer end of the piston chamber 13. The valve plate 19 is secured in place upon the block 12 by the head 17, utilizing the annular rim 22. Specifically, the rim 22 is arranged in an annular recess 24 formed in the adjacent surface of the head 17 disposed about the inner end of the exhaust cavity 18; whereby the rim 22 is clamped in place between the block 12 and the head 17. The valve plate 19 constitutes a common dividing wall between the outer end of the piston chamber 13 and the exhaust cavity 18 and has a pair of elongated and oppositely disposed exhaust ports 25 formed therein and communicating between the explosion dome 23 and the exhaust cavity 18. Also, a threaded opening 26 is formed in the side wall 21 in one of the webs between the two adjacent exhaust ports 25, and receives the threaded inner end of a fuel injection nozzle 27 that also extends through a communicating opening 28 formed in the head 17, the opening 28 being suitably packed, in a manner not shown. Thus it will be understood that the nozzle 27 projects in packed relation through the opening 28 formed in the head 17 and thence through the exhaust cavity 18 into the threaded opening 26 and communicates with the explosion dome 23.

The valve mechanism 11 further comprises a movable valve element 29 also arranged in the exhaust cavity 18 and cooperating with the valve plate 19, the valve element 29 having a substantially inverted cup-shape and including a top wall 30 and a side wall 31. The valve element 29 is carried by the inner end of an elongated valve stem 32 projecting into the exhaust cavity 18 and secured to the top wall 30. Preferably the valve element 29 and the valve stem 32 are formed of one-piece integral construction of an appropriate temperature-resistant steel. The valve element 29 has a cavity 33 formed therein that is adapted to receive the adjacent portion of the valve plate 19; and specically the interior surface of the side wall 31 is provided with two spaced-apart and inwardly directed rings 34 and 35 respectively disposed in lower and upper positions and respectively provided with smooth ground seating surfaces 36 and 37 that cooperate with a smooth ground seating surface 38 provided on the exterior of the side wall 21 of the valve plate 19.

The valve element 29 is movable into open and closed positions with respect to the valve plate 19, whereby the seating surfaces 36 and 37 respectively disengage and engage the cooperating seating surface 38. More particularly, when the valve element 29 is moved into its closed position with respect to the valve plate 19, the seating surfaces 36 and 37 respectively engage the seating surface 38 upon lower and upper sections thereof respectively disposed below and above the two exhaust ports 25, for the purpose of closing and sealing the exhaust ports 25. Also a substantially U-shaped slot 39 is formed in the side wall 31 of the valve element 29 in order to accommodate the fuel nozzle 27; and a pair of inwardly directed ribs 46 are disposed on opposite sides of the slot 39 and joining the rings 34 and 35, the ribs 40 being provided with seating surfaces 41 joining the seating surfaces 36 and 37 so as to prevent the escape of pressure through the slot 39 when the valve element 29 occupies its closed position. In the arrangement, the seating surfaces 36, 37, 38 and 41 are tapered inwardly toward the center line of the valve stem 32 and upwardly away from the adjacent outer end of the piston chamber 13 at an angle of about 8 to 10 so as to obtain adequate seating and sealing of the seating surfaces mentioned, without sticking thereof.

The valve stem 32 is slidably mounted in a central opening provided in a tubular member 42 carried by an annular plate 43 secured to the head 17 and closing the outer end of the exhaust cavity 18, the plate 43 being removably secured in place by any suitable arrangement, not shown. The inner end of the valve stem 32 projects through the opening mentioned formed in the tubular member 42 into the exhaust cavity 18, as previously noted; while the outer end of the valve stem 32 projects well above the outer end of the tubular member 42. Also an annular plate 44 is removably secured by any suitable means, not shown, to the annular plate 43, and terminates in an upstanding tubular barrel 45. An upstanding substantially inverted cup-shaped casing 46 is slidably supported upon the barrel 45, the casing 46 terminating in an outerend Wall 47 having a centrally disposed opening formed therein through which the outer end of the valve stem 32 projects. Thus the valve stem 32 is mounted for longitudinal sliding movements upon the tubular member 42; and the casing 46 is mounted for longitudinal sliding movements upon the barrel 45. The barrel 45 surrounds the tubular member 42 in spaced relation therewith defining an upstanding chamber therebetween, the outer end of the barrel 45 extending well above the outer end of the tubular member 42. A helical spring 48 is arranged within the barrel 45 and the casing 46, the lower end of the spring 48 being disposed between the tubular member 42 and the barrel 45 and firmly clamped in place in cooperating recesses 49 and 50 respectively formed in the annular plates 44 and 43 in surrounding relation with respect to the tubular member 42, and the upper end of the spring 48 being secured to the end wall 47 of the casing 46 by an arrangement including a pair of cooperating thimbles 51 and 52 threadably engaging each other. More particularly, the thimble 51 surrounds and slidably supports the upper end of the valve stern 32, projects through the central opening formed in the end wall 47 of the casing 46, and carries adjacent to the lower end thereof an annular ange 53 spaced below the end wall 47, the last turn of the upper end of the spring 48 being arranged between the ange 53 and the end wall 47 and securely clamped in place by the cooperation between the thimbles 51 and 52. The thimble 52 carries an annular ange 54 disposed exteriorly of and in clamped relation with the end wall 47. ln order to prevent relative rotation between the thimbles 51 and 52, a resilient anchor spring 55 is carried by the thimble 52 and provided with a projection 56 extending through cooperating and aligned holes respectively formed in the flange 54 and in the end wall 47.

As previously noted, the valve stem 32 is slidable longitudinally within the thimble 51, and in order to prevent complete displacement of the valve stem 32 with respect to the thimble 51, an arrangement is provided that includes a recess 57 formed in the outer end of the valve stem 32 and a substantially U-shaped lock washer 58 carried in the recess 57 and engaging the adjacent end of the thimble 51. Also, a recess 59 is formed in the intermediate portion of the valve stem 32 and carries a pair of split washers 6ft, that, in turn, support an annular collar 61; and a compression spring 62 is arranged between the annular collar 61 and the annular iiange 53 In View of the foregoing, it will be understood that the spring 48 biases the casing 46 upwardly away from the annular plate 44, and that the spring 62 biases the valve stem 32 downwardly with respect to the thimble 51 and consequently with respect to the thimble 52 and the casing 46. f

The casing 46 carries a pair of outwardly and oppositely disposed and longitudinally projecting studs 63 arranged adjacent to the lower end thereof, that, in turn, carry a pair of hardened rollers 64, that cooperate with cam surfaces 65 provided on a pair of longitudinally spacedapart operating cams 66 carried by a longitudinally extending camshaft 67, that is suitably supported in a manner, not shown, by the engine 10. The cams 66 are arranged in proper timed relation upon the camshaft 67 for the purpose of controlling the scavenger valve mechanism 11, in a manner more fully described hereinafter.

In view of the foregoing description of the construction and arrangement of the scavenger valve mechanism 11, it will be understood that during rotation of the camshaft 67, the cam surfaces 65 on the cams 66 riding upon the rollers 64 depress or move the casing 46 from its normal position, illutrated at Fig. l, into its operated position, whereby the casing 46 sliding upon the barrel 45 compresses the spring 48. Also the movement of the casing 46 from its normal position into its operated position effects compression of the spring 62 between the collar 61 and the ange 53, whereby the valve stem 32 is moved from its normal position, illustrated in Fig. 1, -into its operated position, moving the valve element 29 from its open position, illustrated in Fig. 1, into its closed position With respect to the valve plate 19. The travel of the casing 46 is somewhat greater than that of the valve stem 32, so that the valve stem 32 reaches its fully operated position prior to the time that the casing 46 reaches its fully operated position, whereby the spring 62 is further compressed urging the valve stem 32 downwardly into its fully operated position insuring complete seating of the valve element 29 with respect to the valve plate 19. As the cams 66 continue to rotate, the casing 46 is held in its fully operated position for a predetermined time interval by virtue of the shape of the cam surfaces 65. Upon further rotation of the cams 66, the cam surfaces 65 thereof disengage the rollers 64, whereby the casing 46 is released, permitting the spring 48 to restore the casing 46 from its operated position back into its normal position with an exceedingly fast movement. As the casing 46 is moved back into its normal position, the spring 48 is placed under slight tension due to the momentum of the parts, but the casing 46 is quickly returned into its normal position without undue vibration of the casing 46 upon the barrel 45 due to the stiffness of the spring 48 and the normal slight friction between the casing 46 and the barrel 45. Of course, the scavenger valve mechanism 11 is operated cyclically by virtue of the continued rotation of the cam shaft 67, whereby the valve element 29 is operated from its open position into its closed position with a moderately fast action, is then held in its closed position for a predetermined time interval, and is then returned from its closed position back into its open position with an exceedingly fast action. Further, it will be appreciated that the camshaft 67 is rotated in predetermined timed relation with respect to the crankshaft, not shown, of the engine 10, in order to effect proper timing of the cycle of the engine 10.

As previously noted, the diesel engine 10 is of the twocycle type, whereby the piston 14 is driven downwardly in the piston chamber 13 in the explosion cycle; and when the piston 14 reaches a position about 35 before bottom dead-center, the scavenger mechanism 11 is operated into its open position quickly placing the explosion dome 23 into communication with the exhaust cavity 18 through the exhaust ports 25 formed in the valve plate 19 so that the pressure in the piston chamber 13 is quickly relieved into the exhaust passage communicating with the exhaust cavity 18. The piston 14 then continues downwardly a short distance uncovering the intake ports 16 that are connected to a source of compressed air, not shown, in a conventional manner; whereby the compressed air sweeps the piston chamber 13 removing all of the products of combustion therefrom into the associated exhaust passage. The piston 14 then continues further downwardly and then starts upwardly, as

carried by the thimble 51.

the associated crankshaft is rotated. When the piston 14 reaches a position about 2 past bottom dead-center in its upward stroke, the scavenger valve mechanism 11 is operated into its closed position; and when the piston 14 moves further upwardly about 35 beyond bottom deadcenter, it closes the intake ports 16, whereby at this time a fresh charge of air is contained in the piston chamber 13. Further upward movement of the piston 14 effects very high compression of the charge of air contained in the piston chamber 13; and when the piston 14 reaches a position about before top dead-center the fuel pump, not shown, is operated to inject through the fuel nozzle 27, a charge of fuel into the explosion dome 23, whereby the charge of fuel is ignited by virtue of the high temperature of the compressed air in the piston chamber 13. Due to the momentum of the crankshaft, the piston 14 is carried through top dead-center and thel expanding combustion products in the piston chamber 13 drive the piston 14 downwardly in its explosion stroke. Of course, it will be understood that the timing of the engine .10 is appropriate to bring about the two-cycle operation of each of the three pistons 14, etc., in the manner described above, the crankshaft, not shown, of the engine halvng a full load speed of about 1000 to 1200 R. P.

In the operation of the scavenger valve mechanism 11, it will be appreciated that only slight movement of the valve element 29 upwardly away from the valve plate 19 is necessary in order to effect full communication between the explosion dome 23 and the exhaust cavity 18 by virtue of the construction of 4the cooperating elements thereof, whereby the scavenger valve mechanism 11 is of the exceedingly fast full-opening type, as contrasted with the relatively slow-opening characteristic of a conventional scavenger valve mechanism of the poppet type. Moreover, in the construction of the scavenger valve mechanism 11, it will be appreciated that the valve stem 32 is disposed out of the normal path of the ame from the explosion dome 23 through -the exhaust cavity 18 into the associated exhaust passage, thereby eliminating undue heating of the valve stem 32 and the consequent tendency of expansion and warping thereof that is normally encountered in conventional scavenger valve mechanisms of 4the poppet type.

1n view of the foregoing, it is apparent that there has been provided in a diesel engine of the two-cycle type, improved scavenger valve mechanism, whereby the valve element is moved from its open position into its fully closed position with a moderately fast action, and whereby the valve element is moved from its closed position into its fully open position with an exceedingly fast action. Accordingly, the scavenger valve mechanism is particularly well adapted for use in two-cycle diesel engines of the high-speed and high-compression ratio type.

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be understood that various modifications may be made therein, and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

What is claimed is:

l. Valve mechanism for controlling the communication between the outer end of the piston chamber and the exhaust cavity in a two-cycle internal combustion engine; said mechanism comprising a stationary valve plate constituting a common dividing wall between the outer end of the piston chamber and the exhaust cavity and having an exhaust port formed therethrough, a movable valve element arranged in the exhaust cavity exteriorly of the piston chamber and cooperating with said valve plate and movable between open and closed positions with respect thereto, said valve plate and said valve element respectively carrying cooperating seating surfaces that are respectively disengaged and engaged when said valve element occupies its respective open and closed positions, said seating surfaces being disposed exteriorly of the piston chamber, engagement of said seating surfaces closing and sealing said exhaust port, and an actuator for selectively moving said valve element between its open and closed positions.

2. Valve mechanism for controlling the communication between the outer end of the piston chamber and the exhaust cavity in a two-cycle internal combustion engine; said mechanism comprising a substantially inverted cup-shaped stationary valve plate constituting a common dividing wall between piston chamber and the outer end of the the exhaust cavity and having an exhaust port formed therethrough, a substantially inverted cup-shaped movable valve element arranged in the exhaust cavity and cooperating with said valve plate and movable between open and closed positions with respect thereto,

said valve plate and said valve element respectively carrying cooperating seating surfaces upon the respective outer and inner surfaces thereof that are respectively disengaged and engaged when said valve element occupies its respective open and closed positions, engagement of said seating surfaces closing and sealing said exhaust port, and an actuator for selectively moving said valve element between its open and closed positions.

3. The valve mechanism set forth in claim 2, wherein closed positi move said va fully open p 4. The va on with a moderately fast action and to lve element from its closed position into its osition with. an exceedingly fast action. lve mechanlsm set forth 1n claim 3, wherein said exhaust port includes two enlarged sections disposed on opposite s1des of the center line of the piston chamber.

5. The valve mechanism set forth in claim 2, wherein said seating surfaces are disposed at an angle of about 8 to 10 inclined inwardly toward the center line of the piston chambe r and away from the outer end thereof.

6. The valve mechanism set forth in claim 2, wherein said valve plate further includes a surrounding rim accommodating clampmg thereof in its stationary position.

7. Valve mechanism for controlling the communication between the outer end of the piston chamber and the exhaust cavity in a two-cycle internal combustion engine; said mechanism comprising a substantially inverted cup-shaped stationary valve plate constituting a common dividing wall between the outer end of the piston chamber and the exhaust cavity and having an exhaust port formed therethrough, a substantially inverted cup-shaped movable valve element arranged in the exhaust cavity and cooperating with said valve plate and movable between open and closed positions with respect thereto, said valve plate being provided an exterior seating surface, said valve element carrying upon the interior surface thereof two spaced-apart rings respectively provided with seating surfaces respectively interior seating surfaces, said interior disengaglng and engaging said exterior seating surface when said valve element occupies its respective open and closed positions, said interior seating surfaces being respectively disposed on opposite sides of said exhaust port when they engage said exterior seating surface in order to close and seal said exhaust port, and an actuator for selectively moving said valve elemen-t between its open and closed positions.

References Cited in the tile of this patent UNITED STATES PATENTS 

